UnderMine 2

1. 
   Exterminated

   Defeated Selt, Sand Hollow Monarch
   80%
2. 
   Just Desserts

   Defeated Trifle
   62%
3. 
   Ground Down

   Defeated Mortar, Stormspire Monolith
   50%
4. 
   Bagged and Tagged

   Defeated Baggledag's Triad
   54%
5. 
   Lit Up

   Defeated Noori, Umbral Lord
   47%
6. 
   Uprooted

   Defeated Cruciferous, Aetherthief Zealot
   42%
7. 
   Hazardous Materials

   Entered the Royal Laboratories
   82%
8. 
   The Hard Way

   Entered the Delvemore Dungeon
   64%
9. 
   A Dusty Place

   Entered the King's Archives
   63%
10. 
    Hallowed Be Thy Name

    Entered the Halls of Din
    54%
11. 
    House of Order

    Entered the Arcane Sanctum
    47%
12. 
    Astronomer

    Discovered the Book of Moon Phases
    41%
13. 
    Shattered

    Discovered the Frost Whirl
    35%
14. 
    The Book of the Dead

    Discovered the Necronomicon
    22%
15. 
    Written in Gold

    Discovered the Pilfer Credit Ledger
    12%
16. 
    The Universal Language

    Discovered the Wanderer's Tuning Fork
    22%
17. 
    Scene of the Crime

    Discovered the Philosopher's Stone
    41%
18. 
    Alchemical Assistance

    Assisted Beltrame in the Royal Laboratories
    57%
19. 
    No Bun Left Behind

    Freed Black Rabbit from the Delvemore Dungeon
    55%
20. 
    Throne Warmer

    Brought the Thalassa Oriv to the Emissary in the Arcane Sanctum
    26%
21. 
    Bombs, Brains, and Boys

    Completed Rook and Bishop's Assignment in the King's Archives
    42%
22. 
    Loyal To The End

    Completed the Preferred Patronage Participation Program
    58%
23. 
    Bootstrapped

    Completed a run with the Peasant
    20%
24. 
    Unshackled

    Completed a run with Black Rabbit
    18%
25. 
    Through Fire and Flames

    Completed a run with Inquisitor Danté
    14%
26. 
    Chest Pain

    Survived Portimer's Planar Chest and Defeated the Mother of Mimics
    27%
27. 
    Smelt You Later

    Forged a Relic or Arcana at the Abandoned Foundry
    48%
28. 
    Formula for Disaster

    Brewed a Potion at the Royal Testing Apparatus
    23%
29. 
    Lexiconnoisseur

    Exchanged a Book at the Tomevault
    32%
30. 
    A New Safety Record

    Accomplished 3 Days without Incident
    31%
31. 
    Synthesis

    Discovered a Combo Item
    33%
32. 
    A Place to Kick BackSecret

    Steam withholds the description of a secret achievement.
    9.6%
33. 
    Three Minutes to Midnight

    Discovered the Penumbra layer of The Well
    25%
34. 
    Doomsday

    Discovered the Umbra layer of The Well
    13%
35. 
    Collapse of Reality

    Discovered the Eclipse layer of The Well
    9.1%
36. 
    Toss a Coin

    Defeated a boss with the shockwave of a Swindler's Coin
    1.1%
37. 
    Almost a Millionaire

    Held 999,999 gold at one time
    4.9%
38. 
    Mondo, dude!

    Selected your starter Mondo
    24%
39. 
    Treasure on Demand

    Captured a Mimic of any type with the Master Mondo
    1.1%
40. 
    Sharpshooter

    Scored 30 points or more in Black Rabbit's Slingshot Gallery
    2.0%
41. 
    Brave the Storm

    Discovered Crackle's egg
    15%
42. 
    Brave the Heat

    Discovered Clockwork's egg
    14%
43. 
    Maximum Power

    Unlocked all of a familiar's abilities
    15%
44. 
    Graduation DaySecret

    Steam withholds the description of a secret achievement.
    16%
45. 
    Frog Stomped

    Defeated Bul & Gogi
    33%
46. 
    Yearn for the Mine!

    Entered the Goldmine
    27%
47. 
    Brave the Light

    Discovered Regin's egg
    15%
48. 
    Brave the Darkness

    Discovered Thresh's egg
    12%
49. 
    Grim and Bear It

    Completed a run with a Grim level of 30 or more
    1.1%
50. 
    Eclipsed

    Completed a run with Minerva
    3.9%
51. 
    Decrystallized

    Reversed Cruciferous' curse and rescued Minerva
    8.2%
52. 
    Master Zoologist

    See every enemy in the Bestiary
    0.1%
53. 
    Royal Archivist

    Gild every Relic and Arcana in the Journal
    0.1%
54. 
    Enlightened

    Discovered Order, Primordial Impetus
    9.9%
55. 
    Cursed

    Discovered Sho'guul, Opulent Demon
    6.1%
56. 
    Planes Walker

    Discovered Sho'guul and Order in a single run
    3.6%

Names, descriptions and icons are the game’s own, as Steam publishes them; the share is how many owners have unlocked each, from Steam's global figures for 56 of them.